The prevalence of human obesity has increased dramatically during the last 2-3 decades in all industrialized and urbanized countries, and obesity is an emerging health threat also to people in developing countries adopting Western life-style and food habits. There are no indications that the present world-wide obesity epidemic is under control, and there are no indications of change to the better in the current trend.
Obesity has a number of consequences for human health, such as age related metabolic decline, insulin resistance, type 2 diabetes, cardiovascular disease, stroke, metabolic syndrome and early, sudden death.
The obvious cause of obesity is a net imbalance over time in the dietary energy intake and the body's energy expenditure. When people consume more energy than they expend, the excess will be stored as fat. The physiological and medical consequence of such energy imbalance is worsened by a sedentary lifestyle and by over-eating of foods rich in sugars and saturated fat.
Visceral obesity is a much higher risk factor for mortality in humans than general obesity; a strong correlation exists between obesity related diseases and visceral fat accumulation. Individuals accumulating much visceral fat and who develop a pattern of fat distribution clinically known as central obesity or abdominal obesity, are for instance particularly prone to developing diabetes (D. Callagher et al. Adipose tissue distribution is different in type 2 diabetes. American Journal of Clinical Nutrition 2009; 89: 807-814). A direct causal link between diabetes and visceral fat accumulation has been shown by studying the effects of surgical removal of visceral fat (Barzilai, N. and G. Gupta. Interaction between Aging and Syndrome X: New Insights on the Pathophysiology of Fat Distribution. Annals New York Academy of Sciences 1999; 58-72; D. M. Huffman, N. Barzilai, Role of visceral adipose tissue in aging, Biochim. Biophys. Acta 1790, 2009: 1117-1123). Such studies have demonstrated that visceral adipose tissue is metabolically very active and plays a predominant role in the development of obesity related health problems, and that gene expression in subcutaneous fat tissue is under control by the visceral adipose tissue. To control and reduce the health impacts of the world-wide obesity epidemic, particular attention should accordingly be paid to finding ways to counteract the development of central body obesity and accumulation of visceral fat.
There is no doubt among health professionals that healthier life-style and improved general nutrition would have the greatest positive impacts on obesity related diseases. Besides a sedentary life style, the amount of food consumed and the nature of carbohydrates and lipids used in Western foods have most often been blamed for the current obesity epidemics. But it has been difficult to predict how individual dietary components would affect the pattern of fat accumulation in the body and obesity related diseases. It has for instance been almost impossible for experts in the field to predict, based on best available knowledge in biochemistry and physiology, that consumption of fructose-sweetened, but not glucose-sweetened, beverages would promote dyslipidemia and lead to increased visceral adiposity and decreased insulin sensitivity in obese humans (K. L. Stanhope et al. Consuming fructose-sweetened, not glucose-sweetened, beverages increase visceral adiposity and lipids and decrease insulin sensitivity in overweight/obese humans. J. Clin. Invest. 2009; 119 (5):1322-1334). The current knowledge on what is determining the pattern of fat accumulation inside the body has first and foremost been developed as a result of experience. This applies also to the accumulating evidence for a correlation between obesity related diseases and the ratio of n-6/n-3 fatty acids in dietary lipids. When this ratio is too high, such as it is in Western diets, the impacts on human health are negative (A. P. Simpoulos. The importance of the Omega-6/Omega-3 Fatty Acid Ratio in Cardiovascular Disease and Other Chronic Diseases. Society for Experimental Biology and Medicine 2008; 674-688; G. Ailhaud et al. An emerging risk factor for obesity: does disequilibrium of polyunsaturated fatty acid metabolism contribute to excessive adipose tissue development? British Journal of Nutrition 2008; 100:461-470), in particular if a high proportion of the n-6 fatty acids in the diet consists of the “essential fatty acid” linoleic acid (C18:3n-6).
In Western diets the ratio of n-6/n-3 fatty acids ratio may be as high as 15/1, whereas this ratio most probably was around 1/1 in the diet human beings have evolved on, and which has shaped our nutrition-related genetic make-up. Nutritionists therefore recommend counteracting the negative impacts of Western diets by enriching food with plant oils, or marine oils, rich in n-3 fatty acids, thereby bringing the dietary n-6/n-3 ratio closer to what human beings have become genetically adapted to. Oils rich in n-3 fatty acids, both marine oils and plant oils, can be used to adjust the n-6/n-3 balance of dietary lipids in a more healthy direction.
In 1993, Belzung and co-authors published nutritional studies comparing the pattern of fat accumulation in Wistar rats fed high fat diets (20% w/w) having n-6/n-3 fatty acids ratios of 6.85/1 (1:1 mixture of beef tallow and olive oil), 0.3/1 (herring oil) and 0.14/1 (a concentrate of EPA (eicosapentaenoic acid=C20:5n-3) and DHA (docosahexaenoic acid=C22:6n-3) (F. Belzung et al. Fish oil n-3 fatty acids selectively limit the hypertrophy of abdominal fat depots in growing rats fed high-fat diets. The American Physiological Society 1993; R1111-R1118). They showed that the animals grew the same on all of these three high fat diets and that their subcutaneous and mesenteric adipose tissues were not affected. However, the animals fed herring oil or EPA/DHA concentrate in stead of beef tallow/olive oil, accumulated less abdominal adipose tissue than those fed the mixture of beef tallow and olive oil. The authors speculated that the differences they could observe were related to the highly different metabolism of these three lipid sources, including diet induced differences in the animals' membrane fatty acid composition and differences in fatty acid synthesis, prostaglandin production and modulation of hepatic enzyme activities. It should be noted that omega-3 constituted as much as 40% (used as concentrate) and 20% (herring oil) of the total dietary lipid (>20% w/w) in these studies, corresponding to a daily intake of omega-3 in the range of 0.7 to 1.4 grams. In studies with rats on the effect of EPA or DHA on expression of genes involved in lipid and glucose metabolism in white adipose tissues (T. Raclot et al. Site-specific regulation of gene expression by n-3 polyunsaturated fatty acids in rat white adipose tissues. Journal of Lipid Research 1997; 38:1963-1971), the daily intake of these fatty acids was 0.9 grams. In conclusion, Wistar rats consuming very high amounts of fish oil or concentrated omega-3, accumulate less visceral fat than rats feeding on a beef tallow/olive oil diet.
Despite our knowledge on the importance of life-style and nutrition on human health, the psycho-sociological obstacles are high when it comes to willingness to change bad habits. It is particularly difficult to change established food priorities in a society, even among people who understand and accept that their life-style and food habits are unhealthy. In this situation it may be desirable to have several strategies, complementary to insisting that people must change their entire way of life, which can be implemented to counteract the current obesity epidemics, in particular visceral obesity resulting in diabetes and other health problems. Pharmaceutical drugs against diabetes exist, but there are no drugs that act by primarily inhibiting the accumulation of visceral adipose tissue, known to be involved in development of diabetes 2 and other diseases. Anti-diabetic drugs in the group called thiazolidinediones works for instance by increasing the body's sensitivity to insulin, and is used in combination with diet and exercise to treat type 2 diabetes. However, these drugs lead to increased whole-body adiposity, a paradox in light of the general understanding that visceral adiposity is a conditioning factor in diabetes 2 development. Drugs in the statin group have been considered for prevention of obesity and diabetes, because drugs in this group inhibit weight gain and fat accumulation. However, they do not inhibit visceral adiposity selectively and their anti-obesity mode of action is apparently related to their ability to enhance respiratory oxygen consumption and metabolic degradation of fat.
The oil composition of the present invention is accordingly highly needed, particularly since it is without toxic side effects, as it decreases the accumulation of visceral fat even when used as a minor supplement to existing high fat Western type diets.